IC die power connection using canted coil spring

ABSTRACT

A semiconductor device assembly according to the present invention may comprise a semiconductor die having at least one contact pad thereon and a package substrate having at least one lead pad thereon. The package substrate is sized to receive the semiconductor die so that the contact pad on the semiconductor die is substantially aligned with the lead pad on the package substrate when the semiconductor die is positioned on the package substrate. A coil spring is positioned between the contact pad on the semiconductor die and the lead pad on the package substrate so that the axis of the coil spring is substantially parallel to the contact pad contained on the semiconductor die and the lead pad contained on the package substrate.

FIELD OF INVENTION

[0001] This invention relates to packaging devices for semiconductor diein general and more specifically to electrical conductors for connectinga semiconductor die to leads contained in a semiconductor packagesubstrate.

BACKGROUND

[0002] Semiconductor devices or die are typically contained within alarger housing or “package” which provides mechanical support for thesemiconductor die also protects it from physical damage. A typicalsemiconductor package includes an area sized to receive thesemiconductor die, commonly referred to as a “window” and is providedwith one or more (and typically tens or hundreds) of leads or circuitpaths which allow the semiconductor die placed within the window of thepackage to be electrically connected to leads or terminals located onexterior portions of the package. The resulting semiconductor deviceassembly (i.e., the package and die) may then be mounted to a suitableprinted circuit board (PCB) by any of a wide range of processes wellknown in the art.

[0003] Several different methods have been developed over the years toelectrically connect the various input or output (I/O) terminals or“pads” on the semiconductor die to the corresponding leads provided onthe package substrate. For example, one method, generically referred toas wire bonding, individually connects each of the I/O pads on the diewith the various leads provided on the package with a very fine wire(e.g., wire having a diameter of about 18 microns or so). The wires arebonded or welded, one at a time, to the pads on the semiconductor dieand on the package substrate using a special tool, such as a wedge or acapillary, and a combination of heat, pressure, and/or ultrasonicenergy. These processes are generically referred to as thermocompressionor thermosonic bonding.

[0004] Although the wire bonding process was originally done manually,with the operator's skill controlling every aspect of the bondingprocess, it has progressed rapidly to a fully automated process as thedensity of I/O connections has increased. In the automated wire bondingprocess, an automatic wire bonding machine senses the locations of theI/O pads on both the semiconductor die and the package substrate andthen automatically connects the appropriate pads with the fine wire.Such automated wire bonding processes are well-developed and have keptpace with the ever increasing number of connections and shrinking bondpad sizes on the semiconductor die. For example, it is not uncommon tobond semiconductor die requiring 300 connections and having two rows ofalternating perimeter bonding pads with pad sizes as small as 50×50 μm(2×2 mils) with 100 μm (4 mils) between on-row pad centers.

[0005] Other techniques that may be used to electrically connect thesemiconductor die to the package substrate include, but are not limitedto, tape automated bonding (TAB) processes and any of a variety of thenewer so-called “flip chip” processes.

[0006] While the foregoing device architectures and methods forelectrically connecting the semiconductor die to the various leadsprovided on the package substrate work well and are being used,continuing developments in integrated circuit technology are resultingin semiconductor die having an ever increasing number of I/O pads aswell ever increasing and substantial current requirements. For example,a 40 watt device operating at 5 volts requires 8 amperes of supplycurrent, whereas the same device operating at 2 volts requires 20amperes of supply current. Since most die architectures require thatsuch power be provided to the die at locations near the center of thechip, and not at the periphery, where the I/O bond pads are typicallylocated, it has proven difficult to provide the required high currentsupply paths. That is, since the wires used in the wire bonding processare extremely fine (typically about 18 microns in diameter), a singlewire cannot be used to carry the high currents required by some of thenewer, higher powered semiconductor die.

[0007] One method that has been used in the past to overcome the limitedcurrent carrying ability of the bond wires is to utilize a plurality ofwires arranged in parallel to provide redundant supply current andground paths for the semiconductor die. While such parallel redundantwiring techniques are effective from a functional standpoint, theyrequire many redundant bond pad sites, which reduces by a like amountthe number of bond pad sites available for device I/O. Other problemsrelating to the use of multiple redundant bond wires to supply theoperating current to the die include, but are not limited to, problemsrelating to resistive power losses in the wires, high inductance, signalcross-talk, and capacitance effects.

[0008] While the newly developed “flip chip” processes ameliorate someof the foregoing problems by providing shorter die-to-packageconnections, some of the gains are offset by the consequent difficultiesthe flip chip architecture imposes on the wiring contained in thepackage substrate. That is, it is still necessary to provide arelatively large circuit path through the highly nested wiring containedon the package substrate in order to provide the required power andground connections to the face of the semiconductor die. Another problemis that flip chip processes typically require specially designedfabrication devices and jigs which are not currently widely used.

[0009] Consequently, a need remains for semiconductor package assemblycapable of providing the relatively the high currents required by someof the newer, higher powered semiconductor devices while at the sametime minimizing resistive power losses, as well as problems resultingfrom high inductance, signal cross-talk, and capacitance effects thatare typically associated with currently available parallel bond wirearchitectures. Additional advantages could be achieved if such animproved package assembly could be fabricated with currently availablesemiconductor package fabrication devices and jigs.

SUMMARY OF THE INVENTION

[0010] A semiconductor die according to the present invention maycomprise a generally planar substrate having a contact pad positioned onthe first side of the semiconductor die. A coil spring is attached tothe contact pad on the semiconductor die so that the axis of the coilspring is generally parallel to the first side of the semiconductor die.

[0011] A semiconductor device assembly according to the presentinvention may comprise a semiconductor die having at least one contactpad thereon and a package substrate having at least one lead padthereon. The package substrate is sized to receive the semiconductor dieso that the contact pad on the semiconductor die is substantiallyaligned with the lead pad on the package substrate when thesemiconductor die is positioned on the package substrate. A coil springis positioned between the contact pad on the semiconductor die and thelead pad on the package substrate so that the axis of the coil spring issubstantially parallel to the contact pad contained on the semiconductordie and the lead pad contained on the package substrate.

[0012] Also disclosed is a method for connecting a contact pad on asemiconductor die with a lead pad on a package substrate that comprisesthe steps of: Positioning a coil spring having at least one coil on thecontact pad on the semiconductor die; placing the semiconductor dieadjacent the package substrate so that the coil spring is substantiallyaligned with the lead pad on the package substrate; urging thesemiconductor die and package substrate together to compress the coilspring and create a pre-load condition; and holding the semiconductordie in a fixed position with respect to the package substrate so as tomaintain the pre-load condition.

[0013] A method for forming a coil spring on a contact pad according tothe present invention may comprise the steps of: Attaching a proximalend of a wire to the contact pad; moving the wire in three-dimensionalspace to produce a first coil, the first coil extending generallyoutwardly from the contact pad; and attaching the wire to the contactpad.

BRIEF DESCRIPTION OF THE DRAWING

[0014] Illustrative and presently preferred embodiments of the inventionare shown in the accompanying drawing in which:

[0015]FIG. 1 is an enlarged cross-sectional view in elevation of aportion of one embodiment of the semiconductor device assembly accordingto the present invention;

[0016]FIG. 2 is a plan view of one side of a semiconductor die showingthe positions and orientations of a plurality of contact pads formedthereon;

[0017]FIG. 3 is a plan view of a package substrate showing the windowand the positions and orientations of a plurality of lead pads formedthereon;

[0018]FIG. 4 is an enlarged cross-sectional view in elevation of aportion of a second embodiment of the semiconductor device assemblyaccording to the present invention;

[0019]FIG. 5 is an enlarged cross-sectional view in elevation of aportion of a third embodiment of the semiconductor device assemblyaccording to the present invention; and

[0020]FIG. 6 is a plan view of one side of a semiconductor die having analternate arrangement of contact pads formed thereon.

DETAILED DESCRIPTION OF THE INVENTION

[0021] A semiconductor device assembly 10 according to one preferredembodiment of the present invention is best seen in FIGS. 1-3 and maycomprise a semiconductor die 12 which may be provided with one or morecontact pads 14 thereon in order to provide electrical power to thesemiconductor die. The semiconductor device assembly 10 may also includea package or substrate 16 having a recessed area or “window” 18 thereinthat is suitable for receiving the semiconductor die 12, as best seen inFIG. 3. The package or substrate 16 may be provided with one or morelead pads 20 thereon which are sized and positioned so that they will besubstantially aligned with the contact pads 14 contained on thesemiconductor die 12 when the semiconductor die 12 is positioned withinthe window 18 of package 16.

[0022] Each contact pad 14 provided on the semiconductor die 12 iselectrically connected to the corresponding lead pad 20 positioned onthe package or substrate 16 by one or more coil springs 22. Each coilspring 22 may be essentially identical to the others and may comprise acontinuous wire 24 having a proximal end 26 and a distal end 28. Thewire 24 may be helically wound around a spring axis 30 in a mannersimilar to those used to form conventional coil springs. In onepreferred embodiment, the coil spring 22 may be formed “on-the-fly” by aconventional wire bonding machine (not shown). However, in otherembodiments of the invention, the spring 22 may be pre-formed and thenlater attached to the contact pads 14, as will be described in greaterdetail below. It is generally preferred, but not required, that eachspring 22 be attached to the contact pad 14 on the semiconductor die 12.Alternatively, the spring 22 could be attached to the lead pad 20 on thepackage substrate 16.

[0023] If the coil spring 22 is to be formed “on-the-fly” by a wirebonding machine (not shown), the first step in the spring formingprocess is to attach the proximal end 26 of the wire 24 to the contactpad 14 on the semiconductor die 12. The proximal end 26 of the wire 24may be attached to the contact pad 14 according to any convenientprocess known in the wire bonding art, such as, for example, bythermocompression or thermosonic bonding. Thereafter, the capillary (notshown) of the wire bonding machine is moved in three dimensions asnecessary to form the first loop or coil 32 of spring 22. This firstloop or coil 32 may also be attached to the contact pad 14 on thesemiconductor die 12 (e.g., by thermocompression or thermosonicbonding), as best seen in FIG. 1. The wire bonding machine (not shown)may continue to form the individual loops or coils 34 of spring 22,attaching each individual loop or coil 34 to the contact pad 14 on thedie 12 as it is formed. After a sufficient number of coils 34 have beenlaid down on the contact pad 14, the wire bonding machine may break thewire 24 after the last bond, thereby forming the distal end 28 of spring22.

[0024] As will be discussed in greater detail below, it is generallypreferred, but not required, to form the spring 22 so that the variouscoils 34 thereof are canted or angled in the same direction with respectto the spring axis 30. That is, as used herein, the term “canted” refersto spring configurations wherein the coils 34 are always inclined in thesame direction with respect to the spring axis 30. So canting the spring22 allows it to be more easily compressed in the transverse direction(indicated by arrow 44), thereby allowing the spring 22 to be“pre-loaded” during assembly of the semiconductor device assembly 10.Such pre-loading of the spring 22 ensures that substantially all of theindividual coils 34 of spring 22 will make contact with the lead pad 20on the package substrate 16, thereby improving electrical performance.

[0025] After the desired number of springs 22 have been formed andsecured to the various contact pads 14 of the semiconductor die 12, thesemiconductor die 12 may be mounted to the package substrate 16 to formthe completed semiconductor device assembly 10 according to the presentinvention. Briefly, the mounting process may involve the step of firstplacing the die 12 within the window 18 of the package 16. See FIG. 3.Once the die 12 has been properly positioned within the window 18, thesprings 22 will make contact with the various corresponding lead pads 20provided on the package substrate 16. Thereafter, the chuck (not shown)that is used to position the die 12 within the window 18 also may movethe die 12 downward slightly (i.e., toward the package substrate 16) inorder to slightly compress the spring or springs 22. So compressing thespring or springs 22 produces the spring pre-load referred to above. Asuitable die attach material (not shown), such as epoxy, then may beinjected into the space between the die 12 and the package substrate 16in order to secure the die 12 to the package substrate 16 and tomaintain the spring pre-load. At this point, the remaining I/O pads (notshown) contained on the semiconductor die 12 may be attached to theappropriate leads (also not shown) provided on the package substrate 16according to any of a wide range of processes (e.g., wire bonding) thatare well-known in the art.

[0026] A significant advantage of the present invention is that solvesthe problem of providing a high current path to a semiconductor die, butwithout requiring the use of multiple input/output pads on the die toprovide the redundant current paths required for high current operation.Another advantage of the present invention is that the coil springs 22used to provide supply power to the semiconductor die may be positionedat any convenient location on the die 12 where the power is required.The ability to locate the electrical connections at those portions ofthe semiconductor die where the power is required reduces the inductive,signal cross-talk and/or noise problems that are typically associatedwith long wire runs. The relatively short current paths, as well as thelarge number of parallel current paths, that are provided by the springcoils also reduces resistive power losses. Still yet another advantageof the present invention is that the springs 22 may be formed“on-the-fly” by conventional and readily available wire bondingequipment.

[0027] Additional advantages associated with the present inventioninclude the ability to move and remove the semiconductor die 12 withrespect to the package substrate 16. For example, the arrangement of thesprings 22 and lead pads 20 allows the semiconductor die 12 to be movedby a substantial amount with respect to the package substrate 16, yetstill maintain good electrical contact. That is, the present inventionreduces the alignment tolerance required by the power connections,thereby allowing the semiconductor die 12 to be positioned on thepackage substrate 16 based on the alignment requirements of the I/Opads, rather than the alignment requirements of the power and groundpaths. Further, the spring contact method available with the presentinvention allows the die 12 to be removed and/or repositioned many timeswith respect to the package substrate 16, which may be required ordesirable in certain applications.

[0028] Having briefly described the semiconductor device assembly 10, aswell as some of its more significant features and advantages, thevarious embodiments of the semiconductor device assemblies according tothe present invention will now be described in detail. However, beforeproceeding with the description, it should be noted that the term“semiconductor die” as used herein refers to a silicon or othersemiconductor integrated circuit or “chip” that contains circuitry andbond pads on one or more sides of the semiconductor die. The term“semiconductor device assembly” refers to the semiconductor die and theassociated package that contains at least the semiconductor die,including any external package leads, pins, or balls that may be used toconnect the semiconductor device assembly to a socket or to a printedcircuit board. In addition to the architecture described above, thesemiconductor package may also be configured to receive additionalcircuit components, or even other semiconductor die, such as is the casewith the so-called multi-chip module (MCM) architecture. Consequently,the present invention should not be regarded as limited to theparticular package configurations and architectures shown and describedherein.

[0029] With the foregoing considerations in mind, one embodiment 10 of asemiconductor device assembly is best seen in FIGS. 1-3 and may comprisea generally planar semiconductor die 12 having a first or lower surface36 and a second or upper surface 38. It should be noted that the terms“upper” and “lower” as used herein are relative terms only and refer tothe orientations of the surfaces shown in the appended drawing. Sinceother orientations are possible, the terms “upper” and “lower” shouldnot be regarded as limiting the invention. The semiconductor die 12 maybe provided with one or more contact pads 14 on the lower surface 36which, in one preferred embodiment, are utilized to provide power andground paths for the circuitry contained in the semiconductor die 12.See FIG. 2. The contact pads 14 provided on the lower surface 36 of die12 may be metallized according to current practice in order to providean electrically conductive surface. Since any of a wide range of metalsand metal alloys may be used to form the metallized contact pads 14contained on the semiconductor die 12, the present invention should notbe regarded as limited to any particular metallic material formedaccording to any particular process. By way of example, in one preferredembodiment, the contact pads 14 may comprise an aluminum alloy and maybe formed by according to a sputtering process. However, since processesfor forming such metallized contacts on semiconductor die are well knownin the art, and since persons having ordinary skill in the art couldreadily select an appropriate material and process after having becomefamiliar with the teachings of the present invention, the material andprocess that are used to form the metallized contact pads 14 in onepreferred embodiment of the invention will not be described in furtherdetail herein.

[0030] As was briefly described above, the second or upper surface 38 ofdie 12 also may be provided with one or more additional contact or I/Opads (not shown) in order to allow corresponding input and outputsignals to be communicated to and from the circuitry contained on thesemiconductor die 12. However, since I/O pads, as well as processes forforming such I/O pads, are well-known in the art and since a detaileddescription of such pads and forming processes is not necessary in orderto understand or practice the present invention, the I/O pads which maybe provided on the upper surface 38 of die 12 will not be described infurther detail herein.

[0031] The package 16 for receiving the semiconductor die 12 is bestseen in FIG. 3 and may comprise a generally rectangularly shaped member,although other shapes are possible. Alternatively, the package 16 mayeven comprise the type associated with the multi-chip module (MCM)architecture described above. In any event, and regardless of itsparticular configuration or intended application, the package 16 may beprovided with a recessed area or “window” 18 that is sized to receivethe semiconductor die 12 that is to be housed within the package 16. Thepackage 16 also may be provided with one or more lead pads 20 that aresized and spaced within the window 18 so that they will be substantiallyaligned with the contact pads 14 provided on the bottom surface 36 ofthe semiconductor die 12. As was the case for the contact pads 14provided on the semiconductor die 12, the lead pads 20 contained on thepackage 16 may be metallized in order to provide a conductive surface or“pad” suitable for making electrical contact with the springs 22. Any ofa wide range of metals and metal alloys deposited according to any of awide range of processes may be used to form the metallized lead pads 20contained on the package substrate 16. Consequently, the presentinvention should not be regarded as limited to lead pads 20 comprisingany particular metallic material and formed according to any particularprocess. However, by way of example, in one preferred embodiment, thelead pads 20 provided on the package substrate 16 may comprise anickel-gold alloy and may be formed according to a plating process.

[0032] The package substrate 16 may also be provided with any number ofadditional leads (not shown), such as, for example, leads suitable forconnecting with the various I/O pads (also not shown) which may beprovided on the upper surface 38 of semiconductor die 12 in the manneralready described. However, since such semiconductor packages are wellknown in the art and could be easily fabricated by persons havingordinary skill in the art after having become familiar with theteachings of the present invention, the particular semiconductor package16 that may be utilized in one preferred embodiment of the presentinvention will not be described in further detail herein.

[0033] The semiconductor device assembly 10 may be provided with one ormore coil springs 22 which electrically connect the contact pads 14 onthe semiconductor die 12 with the corresponding lead pads 20 provided onthe package substrate 16. For example, in the embodiment shown in FIG.2, the lower surface 36 of semiconductor die 12 is provided with fourseparate contact pads 14 arranged substantially in the form of a “+”symbol. Alternatively, other arrangements are possible, as will bedescribed in greater detail below. Each contact pad 14 has a length 40and a width 42. In one preferred embodiment, the width 42 of eachcontact pad 14 is sufficient to accommodate two coil springs 22positioned side by side, substantially in the manner illustrated in FIG.2. Since it is preferred that the corresponding lead pads 20 provided onthe package substrate 16 have substantially the same size and shape asthe contact pads 14 on the semiconductor die 12, the two springs 22affixed to the contact pad 14 on the semiconductor die 12 will alsocontact substantially the entirety of the lead pad 20 provided on thepackage substrate 16.

[0034] Before proceeding with the description it should be noted thatthe contact pads 14 provided on the semiconductor die 12 may be providedwith any number of springs 22 having any convenient number of individualcoils 34. Generally speaking, the number of individual springs 22, thenumber of coils 34 per spring, and the size (i.e., diameter) of thespring wire 24 should be selected so that the spring 22 will be capableof supplying the current required by the particular semiconductor die12. That is, since each coil 34 of the spring 22 provides two currentpaths between the lead pad 20 and the contact pad 12, a person desiringto practice the present invention should select the foregoing parameters(e.g., number springs 22, number of coils 34 per spring 22, and springwire size) so that each coil 34 can safely carry its portion of theexpected current without danger of overheating.

[0035] By way of example, and without limiting the scope of the presentinvention, in one preferred embodiment, each spring 22 may be formedfrom wire 24 having a diameter in the range of about 20 microns to about30 microns (25 microns preferred). The spring 22 may be formed so thatit includes approximately 10 coils per millimeter, with each coil 34having a diameter in the range of about 100 microns to about 150 microns(125 microns preferred).

[0036] It should also be noted that the particular material comprisingthe wire 24 from which the spring 22 is formed should be selected sothat it is compatible, at least from a metallurgical standpoint, withthe material or materials forming the metallized contact and lead pads14 and 20. Since a wide range of metals and metal alloys may be utilizedto form the metallized contact and lead pads 14 and 20, as well as toform spring 22, and since persons having ordinary skill in the art willreadily recognize those materials that are metallurgically compatibleand those that are not, the present invention should not be regarded aslimited to any particular material or combinations of materials.However, by way of example, in one preferred embodiment, the wire 24used to form spring 22 may comprise gold.

[0037] Continuing now with the description and with reference primarilyto FIG. 1, each coil spring 22 may be essentially identical to theothers and may comprise a continuous wire 24 having a proximal end 26and a distal end 28. The wire 24 is helically wound around a spring axis30 in the manner of a conventional coil spring and, in one preferredembodiment, is formed “on-the-fly” by a wire bonding machine (notshown). The first step in the spring forming process is to attach theproximal end 26 of the wire 24 to the contact pad 14 on thesemiconductor die 12. The proximal end 26 of wire 24 may be attached tothe contact pad 14 by the wire bonding machine (not shown) by any of awide range of processes that are now known in the art (e.g.,thermocompression or thermosonic bonding) or that may be developed inthe future. After the proximal end 26 of wire 24 has been successfullybonded to the contact pad 14, the capillary (not shown) of the wirebonding machine is moved in three dimensions as necessary to form thefirst loop or coil 32 of spring 22. Since the capillary of a wirebonding machine is moveable in three dimensions and since the motionthereof is generally computer controlled, it is a simple matter for auser (not shown) to program the wire bonding machine to form the variousloops or coils 34 of spring 22. That is, since persons having ordinaryskill in the art could readily program a wire bonding machine to formthe coils 34 of the spring 22 after having become familiar with theteachings of the present invention, the particular process that may beused with one particular wire bonding machine to form the spring coils34 will not be described in greater detail below.

[0038] After the first coil 32 is formed, it may also be attached to thecontact pad 14 on the semiconductor die 12 by any convenient bondingprocess (e.g., by thermocompression or thermosonic bonding). The wirebonding machine (not shown) may continue to form the individual loops orcoils 34 of spring 22, attaching each individual coil 34 to the contactpad 14 on the die 12. After a sufficient number of coils 34 have beenlaid down, the wire bonding machine may break the wire 24 after the lastbond, thereby forming the distal end 28 of spring 22.

[0039] As was briefly discussed above, it is generally preferred, butnot required, to form the spring 22 so that the various coils 34 thereofare canted in the same direction with respect to the spring axis 30.That is, all of the individual coils 34 are always inclined in the samedirection with respect to the spring axis 30. For example, in theembodiment shown in FIG. 1, each of the coils 34 is inclined withrespect to the axis 30 so that the coils slope generally downwardly fromleft to right. If the coils were not canted, the “front” portions of thecoils (i.e., the portions of the coils that re closest to the observer)would slope in one direction while the “rear” portions of the coils(i.e., those portions of the coils located behind the front portions)would slope in the opposite direction. Forming the coil spring 22 sothat it is so canted allows the spring 22 to be more easily compressedin the cross or transverse direction (indicated by arrow 44) to producethe desired “pre-load.” As mentioned above, pre-loading the spring 22 inthe transverse direction 44 ensures that substantially all of theindividual coils 34 of spring 22 will make contact with the lead pad 20on the package 16. The amount of cant (i.e., cant angle 46) that may beprovided to the spring 22 is not particularly critical, and any of awide range of cant angles may be regarded as within the scope of thepresent invention. By way of example, in one preferred embodiment, thecant angle 46 may be selected to be in the range of about 45 degrees toabout 75 degrees.

[0040] After the desired number of springs 22 have been formed andsecured to the various contact pads 14 of the semiconductor die 12, thesemiconductor die 12 may be mounted to the package substrate 16 to formthe completed semiconductor device assembly 10 according to the presentinvention. The first step in the mounting process is to place the die 12within the window 18 of the package 16. This step may be performed withthe aid of equipment and devices, such as a chuck (not shown), that areknown in the art for positioning semiconductor die within correspondingpackage windows. Once the die 12 has been positioned within the window18, the various springs 22 provided on the die 12 will make contact withthe various corresponding lead pads 20 provided on the package substrate16. The device (e.g., chuck) used to position the die 12 within thewindow 18 may then urge the die 12 toward the package 16 to introduce aslight amount of “pre-load” in the springs 22. The pre-load helps toensure that substantially all of the loops or coils 34 of the springs 22make good electrical contact with the contact and lead pads 14 and 20.Thereafter, any of a wide range of die attach materials (not shown),such as, for example epoxy, or a polyimide or silicone adhesive, may beinjected into the space between the die 12 and the package 16. The dieattach material secures the die 12 within the package 16, therebyensuring that the spring pre-load is retained. Alternatively, othermethods of applying the die attach material could also be used, as wouldbe obvious to persons having ordinary skill in the art after havingbecome familiar with the teachings of the present invention. Forexample, the die attach material may be deposited on the packagesubstrate 16 before the die 12 is moved into position within the window18. In any event, after the die 12 is secured within the window 18, theremaining I/O pads (not shown) contained on the semiconductor die 12 maybe attached to the appropriate leads (also not shown) provided on thepackage 16 according to any of a wide range of processes (e.g., wirebonding) well-known in the art or that may be developed in the future.

[0041] As described above, the coil spring 22 that is used toelectrically connect the contact pad 14 with the lead pad 20 may beformed “on-the-fly” by a wire bonding machine. However, otherarrangements are possible. For example, with reference now to FIG. 4, asecond embodiment 110 of a semiconductor device assembly may be providedwith a pre-formed coil spring 122. The pre-formed coil spring 122 maythen be attached to the contact pad 114 provided on the semiconductordie 112. In the embodiment shown in FIG. 4, only the proximal and distalends 126 and 128 are bonded to the contact pad 114. The remaining coils134 are urged against both the contact pad 114 and lead pad 120contained on the package substrate 116 by slightly compressing thespring 122 to form the pre-load described above for the firstembodiment. The proximal and distal ends 126 and 128 of pre-formedspring 122 may be bonded to the contact pad 114 by any of a wide rangeof processes (e.g., thermosonic or thermocompression bonding) that arecurrently well-known in the art or that may be developed in the futurefor bonding such materials.

[0042] Still other arrangements are possible. For example, a thirdembodiment 210 of a semiconductor device assembly also may be providedwith a pre-formed coil spring 222, as best seen in FIG. 5. However, inthis third embodiment 210, the pre-formed coil spring 222 may beattached to the contact pad 214 on die 212 by a separate bond wire 223.The bond wire 223 may extend through the various coils 234 of spring 222so that the bond wire 223 is generally parallel to the spring axis 230.The proximal and distal ends 227 and 229 of bond wire 223 may be bondedto the contact pad 214 on die 212 by any of a wide range of processes,such as, for example, by thermosonic or thermocompression bondingtechniques. Since the various coils 234 of the spring 222 are notindividually bonded to either the contact pad 214 or the lead pad 220contained on the package substrate 216, it will usually be necessary toslightly compress the spring 222 during assembly of the semiconductordevice assembly 210 to produce the pre-load described above. The springpre-load helps to ensure that each individual coil 234 of spring 222will make good electrical contact with the respective pads 214 and 220.

[0043] Finally, and as was mentioned above, the various contact pads(e.g., 14) provided on the die (e.g., 12) may comprise any of a widerange of configurations. For example, with reference now to FIG. 6,another embodiment 312 of a semiconductor die may comprise eight (8)individual contact pads 314 arranged substantially as shown in FIG. 6. Asingle spring 322 may be provided on each separate contact pad 314 (onlya single spring 322 is shown in FIG. 6 for clarity). Of course, the leadpads (not shown) provided on a mating package substrate (also not shown)would be arranged in a similar configuration so that the lead pads (notshown) would be substantially aligned with the corresponding contactpads 314 provided on the die 312. The springs 322 provided on eachcontact pad 314 may comprise any of the embodiments shown and describedabove.

[0044] It is contemplated that the inventive concepts herein describedmay be variously otherwise embodied and it is intended that the appendedclaims be construed to include alternative embodiments of the inventionexcept insofar as limited by the prior art.

What is claimed is:
 1. A semiconductor device assembly, comprising: asemiconductor die having at least one contact pad thereon; a packagesubstrate having at least one lead pad thereon, said package substratebeing sized to receive said semiconductor die so that the contact pad onsaid semiconductor die is substantially aligned with the lead pad onsaid package substrate when said semiconductor die is positioned on saidpackage substrate; and a coil spring having an axis, said coil springpositioned between the contact pad on said semiconductor die and thelead pad on said package substrate so that the axis of said coil springis substantially parallel to the contact pad contained on saidsemiconductor die and the lead pad contained on said package substrate.2. The semiconductor device assembly of claim 1 , wherein said coilspring is attached to the contact pad on said semiconductor die.
 3. Thesemiconductor device assembly of claim 2 , wherein said semiconductordie includes a top surface and a bottom surface and wherein the contactpad is located on the bottom surface of said semiconductor die.
 4. Thesemiconductor device assembly of claim 3 , wherein said coil springcomprises at least one coil.
 5. The semiconductor device assembly ofclaim 3 , wherein said coil spring comprises at least two coils.
 6. Thesemiconductor device assembly of claim 5 , wherein at least one of thecoils of said coil spring is attached to the contact pad on saidsemiconductor die.
 7. The semiconductor device assembly of claim 5 ,wherein at least two of the coils of said coil spring are attached tothe contact pad on said semiconductor die.
 8. The semiconductor deviceassembly of claim 1 , wherein said coil spring comprises a proximal endand a distal end, the proximal and distal ends of said coil spring beingattached to the contact pad on said semiconductor die.
 9. Thesemiconductor device assembly of claim 8 , wherein said coil springcomprises at least two coils located between the proximal and distalends.
 10. The semiconductor device assembly of claim 1 , wherein saidcoil spring comprises a proximal end, a distal end, and at least onecoil, said semiconductor device assembly further comprising a bond wirehaving a proximal end and a distal end, said bond wire extending throughthe coil of said coil spring, generally along the axis of said coilspring, the proximal and distal ends of said bond wire being attached tothe contact pad on said semiconductor die, said bond wire securing saidcoil spring to the contact pad of said semiconductor die.
 11. Thesemiconductor device assembly of claim 1 , wherein said coil springcomprises a canted coil spring.
 12. A semiconductor die, comprising: agenerally planar substrate having a first side and a second side; acontact pad positioned on the first side of said semiconductor die; acoil spring having an axis attached to the contact pad on saidsemiconductor die so that the axis of said coil spring is generallyparallel to the first side of said semiconductor die.
 13. Thesemiconductor die of claim 12 , wherein said coil spring has a proximalend and a distal end, and wherein the proximal end of said coil springis attached to the contact pad on said semiconductor die at a firstlocation and wherein the distal end of said coil spring is attached tothe contact pad on said semiconductor die at a second location.
 14. Thesemiconductor die of claim 12 , wherein said coil spring comprises atleast one coil, wherein said at least one coil is attached to thecontact pad on said semiconductor die.
 15. The semiconductor die ofclaim 12 , wherein said coil spring comprises a proximal end, a distalend, and at least one coil, said semiconductor die further comprising abond wire having a proximal end and a distal end, said bond wireextending through the coil of said coil spring, generally along the axisof said coil spring, the proximal and distal ends of said bond wirebeing attached to the contact pad on said semiconductor die, said bondwire securing said coil spring to the contact pad of said semiconductordie.
 16. A method of connecting a contact pad on a semiconductor diewith a lead pad on a package substrate, comprising: positioning a coilspring having at least one coil on the contact pad on the semiconductordie; placing the semiconductor die adjacent the package substrate sothat the coil spring is substantially aligned with the lead pad on thepackage substrate; urging the semiconductor die and package substratetogether to compress the coil spring and create a pre-load condition;and holding the semiconductor die in a fixed position with respect tothe package substrate so as to maintain the pre-load condition.
 17. Amethod for forming a coil spring on a contact pad, comprising: (a)attaching a proximal end of a wire to the contact pad; (b) moving thewire in three-dimensional space to produce a first coil, the first coilextending generally outwardly from the contact pad; and (c) attachingthe wire to the contact pad.
 18. The method of claim 17 , furthercomprising: (d) moving the wire in three-dimensional space to produce asubsequent coil, the subsequent coil extending generally outwardly fromthe contact pad; (e) attaching the wire to the contact pad; andrepeating steps (d) and (e) to form a spring having a desired number ofcoils.
 19. The method of claim 18 , wherein the steps of attaching thewire to the contact pad comprise thermosonic bonding.
 20. The method ofclaim 18 , wherein the steps of attaching the wire to the contact padcomprise thermocompression bonding.